CVE-2022-50260

In the Linux kernel, the following vulnerability has been resolved:

drm/msm: Make .remove and .shutdown HW shutdown consistent

Drivers .remove and .shutdown callbacks are executed on different code paths. The former is called when a device is removed from the bus, while the latter is called at system shutdown time to quiesce the device.

This means that some overlap exists between the two, because both have to take care of properly shutting down the hardware. But currently the logic used in these two callbacks isnt consistent in msm drivers, which could lead to kernel panic.

For example, on .remove the component is deleted and its .unbind callback leads to the hardware being shutdown but only if the DRM device has been marked as registered.

That check doesnt exist in the .shutdown logic and this can lead to the driver calling drm_atomic_helper_shutdown() for a DRM device that hasnt been properly initialized.

A situation like this can happen if drivers for expected sub-devices fail to probe, since the .bind callback will never be executed. If that is the case, drm_atomic_helper_shutdown() will attempt to take mutexes that are only initialized if drm_mode_config_init() is called during a device bind.

This bug was attempted to be fixed in commit 623f279c7781 (drm/msm: fix shutdown hook in case GPU components failed to bind), but unfortunately it still happens in some cases as the one mentioned above, i.e:

systemd-shutdown[1]: Powering off. kvm: exiting hardware virtualization platform wifi-firmware.0: Removing from iommu group 12 platform video-firmware.0: Removing from iommu group 10 ————[ cut here ]———— WARNING: CPU: 6 PID: 1 at drivers/gpu/drm/drm_modeset_lock.c:317 drm_modeset_lock_all_ctx+0x3c4/0x3d0 … Hardware name: Google CoachZ (rev3+) (DT) pstate: a0400009 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=–) pc : drm_modeset_lock_all_ctx+0x3c4/0x3d0 lr : drm_modeset_lock_all_ctx+0x48/0x3d0 sp : ffff80000805bb80 x29: ffff80000805bb80 x28: ffff327c00128000 x27: 0000000000000000 x26: 0000000000000000 x25: 0000000000000001 x24: ffffc95d820ec030 x23: ffff327c00bbd090 x22: ffffc95d8215eca0 x21: ffff327c039c5800 x20: ffff327c039c5988 x19: ffff80000805bbe8 x18: 0000000000000034 x17: 000000040044ffff x16: ffffc95d80cac920 x15: 0000000000000000 x14: 0000000000000315 x13: 0000000000000315 x12: 0000000000000000 x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000 x8 : ffff80000805bc28 x7 : 0000000000000000 x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000 x2 : ffff327c00128000 x1 : 0000000000000000 x0 : ffff327c039c59b0 Call trace: drm_modeset_lock_all_ctx+0x3c4/0x3d0 drm_atomic_helper_shutdown+0x70/0x134 msm_drv_shutdown+0x30/0x40 platform_shutdown+0x28/0x40 device_shutdown+0x148/0x350 kernel_power_off+0x38/0x80 __do_sys_reboot+0x288/0x2c0 __arm64_sys_reboot+0x28/0x34 invoke_syscall+0x48/0x114 el0_svc_common.constprop.0+0x44/0xec do_el0_svc+0x2c/0xc0 el0_svc+0x2c/0x84 el0t_64_sync_handler+0x11c/0x150 el0t_64_sync+0x18c/0x190 —[ end trace 0000000000000000 ]— Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018 Mem abort info: ESR = 0x0000000096000004 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault Data abort info: ISV = 0, ISS = 0x00000004 CM = 0, WnR = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=000000010eab1000 [0000000000000018] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 96000004 [#1] PREEMPT SMP … Hardware name: Google CoachZ (rev3+) (DT) pstate: a0400009 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=–) pc : ww_mutex_lock+0x28/0x32c lr : drm_modeset_lock_all_ctx+0x1b0/0x3d0 sp : ffff80000805bb50 x29: ffff80000805bb50 x28: ffff327c00128000 x27: 0000000000000000 x26: 00000 —truncated—

Affected Software

References

• https://git.kernel.org/stable/c/0a58d2ae572adaec8d046f8d35b40c2c32ac7468
• https://git.kernel.org/stable/c/0e6649a2e31ac157c711d583ec8f5ec59da5de0e
• https://git.kernel.org/stable/c/26f9a766f87b33c50ed400a9500cc1dc9aced953